Marines from 4th Combat Engineer Battalion, prepare to enter a building through a window during pre-mobilization and annual training at Quantico’s Combat Town on Feb. 20. Military Operations on Urban Terrain training helps units learn firsthand about different tactics and techniques in urban terrain within the operating forces. - Marines from 4th Combat Engineer Battalion, prepare to enter a building through a window during pre-mobilization and annual training at Quantico’s Combat Town on Feb. 20. Military Operations on Urban Terrain training helps units learn firsthand about different tactics and techniques in urban terrain within the operating forces.